Enhanced electrical and thermal conductivity of modified poly(acrylonitrile-co-butadiene)-based nanofluid containing functional carbon black-graphene oxide

Solution refluxing and high-pressure homogenization technique were reported for synthesizing nanofluids based on modified poly(acrylonitrile-co-butadiene) (M-PANB) as base fluid and carbon black (CB)/carbon black-graphene oxide (CB-GO) as filler. The physiochemical properties were studied to analyze the structure, morphology, thermal and electrical conductivity. FTIR analysis corroborated the structure of CB-GO nanobifiller and nanocomposite. Microstructure analysis of M-PANB/CB-GO revealed good dispersion of CB-GO nanosheets, while CB series showed granular distribution. XRD studies confirmed amorphous structure of M-PANB/CB-GO nanocomposite. Thermal conductivity of nanofluid was found to increase upto 1.41 W/mK for 10 wt.% CB-GO loading and electrical conductivity was increased to 2.5 × 10^?3 Scm^?1.     

多感官设计的可视化分析:研究进展、热点与趋势

目的 对国内多感官设计的相关文献进行总结分析,探寻该领域的研究现状、热点与发展趋势,为今后多感官设计理论及实践研究提供参考。方法 基于文献计量分析法,以2005-2021年知网、万方、维普、超星及华艺数据库收录的741篇多感官设计文献为分析对象,采用CiteSpace、NoteExperss等软件对该领域文献的发表时间、载文期刊、高被引文献、作者、机构、     

Sources of inspiration? Making sense of scientific references in patents

Scientific references in patent documents can be used as indicators signaling science-technology interactions. Whether they reflect a direct ‘knowledge flow’ from science to technology is subject of debate. Based on 33 interviews with inventors at Belgian firms and knowledge-generating institutes active in nanotechnology, biotechnology and life sciences, we analyze the extent to which scientific references in patents reflect sources of inspiration. Our results indicate that scientific knowledge acts as a source of inspiration for about 50 % of the inventions. At the same time, the scientific references cited in patent documents and available in patent databases do not provide an accurate picture in this respect: 30 % of patents that were inspired by scientific knowledge do not contain any scientific references. Moreover, if scientific references are present, half of them are evaluated as unimportant or background information by the inventor. Overall, these observations provide evidence that scientific references in patent documents signal relatedness with the implied inventions without necessarily implying a direct, inspirational, knowledge flow between both activity realms.     

Laser Ablation Process Competency to Fabricate Microchannels in Titanium Alloy

Laser ablation is one of the competent machining processes to fabricate microfeatures in variety of engineering materials. This study has been progressed to evaluate the process capability of generating microchannels of various sizes (50 × 50 µm, 100 × 100 µm, 200 × 100 µm, and 1000 × 500 µm) in titanium alloy (Ti6Al4V) using Nd:YAG laser. Channel's top width, bottom width, depth, and taperness are examined as the four process responses against three laser based parameters to the naming of laser intensity, repetition rate, and scan speed. All the geometrical dimensions are measured through photographic snapshots of SEM of each fabricated channel. The results reveal that the selection of channel size is critical to achieve the desired machining geometries. Wider sized channels (such as 200 × 100 and 500 × 1000 µm) are experienced as more flexible to be generated than narrower sized channels (50 × 50 and 100 × 100 µm). The precise parametric combination is the key to realize more tight dimensional enormities with respect to the targeted machining elements. The most appropriate parametric combinations that can generate the respectable results are explored and applied for machining of different channel sizes.     

In situ microfibrillar morphology and properties of polypropylene/polyamide/carbon black composites prepared through multistage stretching extrusion

Isotactic polypropylene/polyamide/carbon black (PP/PA/CB) composites with microfibrillar morphology were designed and prepared using a multistage stretching extruder with an assembly of laminating-multiplying elements (LMEs). CB was selectively located in PA. With the increase of LME number from zero to seven, the conductive PA/CB phase was found to experience an elongating-breaking-elongating process. This morphological development resulted in the strong dependence of electrical resistivity on the LME number. When no LME was used, PP/PA/CB materials with 2.0, 3.0, or 4.0 wt% (1.0, 1.6, and 2.1 vol%) CB employed were insulators (resistivity: 10¹⁰ Ω cm) due to their droplet morphology. With the introduction of LMEs, a conductive network was formed because of the microfibrillation of the conductive PA/CB phase; these materials became conductors (resistivity: 10⁴–10⁶ Ω cm). The percolation threshold can lower to 1.5 wt% (0.9 vol%). The low resisticity and percolation threshold cannot be obtained through the conventional method.     

Fiber distribution and orientation in UHP-FRC beams and their effect on backward analysis

In this study 23 ultra-high performance fiber reinforced concrete (UHP-FRC) notched beams were tested in order to investigate the effect of fiber orientation and distribution on the bending behavior. Due to the small fiber diameter and high fiber volume fraction used in UHP-FRC, the number of fibers crossing a 150 × 150 mm (6 × 6 in.) beam section can be as high as 26,000. An opto-analytical method was used to investigate the number and orientation of the fibers near the critical crack in each test beam. For the casting method used, which was in accordance with the recommendation of Association Francaise de Genie Civil (AFGC) and Service d’etudes techniques des routes et autoroutes (SETRA), a high degree of uniformity in fiber distribution and orientation was found over the beam cross section. Based on the analytically determined fiber orientation and distribution, shape functions were derived that take into account variations over the beam height. The proposed shape functions were incorporated in a backward analysis of the results from bending tests to estimate the uniaxial tensile behavior of the UHP-FRC used. The sensitivity of the backwardly calculated tensile behavior of UHP-FRC to variations in fiber density and orientation was evaluated. Based on the bending test results of the notched beam specimens, and for the casting method used in this research, the influence of these variations on the backwardly calculated tensile strength was found to be small, with a maximum stress variation of ~5 % for any given crack width.     

Probability Health Risk Assessment and Measurement Uncertainty Estimation Related to Internal Exposure to Natural Radionuclides from Soil

The purpose of this paper was to develop methodology and to assess cancer mortality risks with assigned measurement uncertainty related to lifetime internal exposure to natural radionuclides ²³⁸U and ²³²Th from soil. Included exposure pathways were inhalation and direct ingestion of dust particles originating from soil. Total of 80 samples were collected at 23 locations that belong to meteorological stations under control of Republic Hydrometeorological Service of Serbia. Activity concentration of radionuclides was measured using HPGe detector. Probability risk assessment and measurement uncertainty analysis was conducted using Monte Carlo method. For location with highest measured activity concentration, assessed cancer mortality risk for ²³⁸U is 0.185 × 10^?6 with coverage interval of (0.0184–0.702) × 10^?6 for ingestion exposure and 0.179 × 10^?6 with coverage interval of (0.00514–1.33) × 10^?6 for inhalation exposure. Mean value for assessed cancer mortality risk for ²³²Th is 0.582 × 10^?6 with coverage interval of (0.0222–2.79) × 10^?6 for ingestion exposure and 1.11 × 10^?6 with coverage interval of (0.0319–8.27) × 10^?6 for inhalation exposure. Coverage interval contains the value of assessed risk with the probability of 95 %. Assessed risks in this paper have low priority for further investigation because they are equal or lower than 10^?6. Probability risk assessment introduces uncertainty analysis in convenient way and enables researches and decision-makers to improve quality of their results and decisions.     

Effect of annealing time on the structural,optical and electrical characteristics of DC sputtered ITO thin films

Using an Indium tin oxide (ITO) ceramic target (In₂O₃:SnO₂, 90:10 wt%), ITO thin films were deposited by conventional direct current magnetron sputtering technique onto glass substrates at room temperature. The obtained ITO films were annealed at 400 °C for different annealing times (1, 2, 5, 7, and 9 h). The effect of annealing time on their structural, optical and electrical properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microcopy (AFM), ultra violet–visible (UV–Vis) spectrometer, and temperature dependence Hall measurements. XRD data of obtained ITO films reveal that the films were polycrystalline with cubic structure and exhibit (222), (400) and (440) crystallographic planes of In₂O₃. AFM and Scanning Electron Microscopy SEM have been used to probe the surface roughness and the morphology of the films. The refractive index (n), thickness and porosity (%) of the films were evaluated from transmittance spectra obtained in the range 350–700 nm by UV–Vis. The optical band gap of ITO film was found to be varying from 3.35 to 3.47 eV with the annealing time. The annealing time dependence of resistivity, carrier concentration, carrier mobility, sheet resistance, and figure of merit values of the films at room temperature were discussed. The carrier concentration of the films increased from 1.21 × 10²⁰ to 1.90 × 10²⁰ cm^?3, the Hall mobility increased from 11.38 to 18 cm² V^?1 s^?1 and electrical resistivity decreased from 3.97 × 10^?3 to 2.13 × 10^?3 Ω cm with the increase of annealing time from 1 to 9 h. Additionally, the temperature dependence of the carrier concentration, and carrier mobility for the as-deposited and 400 °C annealed ITO films for 2 and 9 h were analysed in the temperature range of 80–350 K.     

Influence of proceedings papers on citation impact in seven sub-fields of sustainable energy research 2005–2011

This paper analyses the following seven sub-fields of Sustainable Energy Research with respect to the influence of proceedings papers on citation patterns across citing and cited document types, overall sub-field and document type impacts and citedness: the Wind Power, Renewable Energy, Solar and Wave Energy, Geo-thermal, Bio-fuel and Bio-mass energy sub-fields. The analyses cover peer reviewed research and review articles as well as two kinds of proceeding papers from conferences published 2005–2009 in (a) book series or volumes and (b) special journal issues excluding meeting abstracts cited 2005–2011 through Web of Science. Central findings are: The distribution across document types of cited versus citing documents is highly asymmetric. Predominantly proceedings papers from both proceeding volumes as well as published in journals cite research articles (60–76 %). Largely, journal-based proceedings papers are cited rather than papers published in book series or volumes and have field impacts corresponding to research articles. With decreasing proceedings paper dominance in research fields the ratio of proceeding paper volumes over journal-based proceedings papers decreases significantly and the percentage of proceedings papers in journals citing journal-based proceedings papers over all publications citing journal-based proceedings papers decreases significantly (from 26.3 % in Wind Power to 4 % in Bio Fuel). Further, the segment of all kinds of proceedings papers (the combined proceedings paper types) citing all proceedings papers over all publications citing all kinds of proceedings papers decreases significantly (from 36.1 % in Wind Power to 11.3 % in Bio Fuel). Simultaneously the field citedness increases across the seven research fields. The distribution of citations from review articles shows that novel knowledge essentially derives directly from research articles (53–72 %)—to a much less extent from proceedings publications published in journals (9–13 %).     

Accuracy verification of a simple local three-dimensional displacement measurement method of DIC with two images coordinates

There are two methods applied for three-dimensional digital image correlation method to measure three-dimensional displacement. One is to measure the spatial coordinates of measuring points by analyzing the images. Then, the displacement vectors of these points can be calculated using the spatial coordinates of these points obtained at different stages. The other is to calibrate the parameters for individual measuring points locally. Then, the local displacements of these points can be measured directly. This study proposes a simple local three-dimensional displacement measurement method. Without any complicated distortion correction processes, this method can be used to measure small displacement in the three-dimensional space through a simple calibration process. A laboratory experiment and field experiment are carried out to prove the accuracy of this proposed method. Laboratory test errors of one-dimensional experiment are similar to the accuracy of the XYZ table; the error in Z-direction is only 0.0025% of the object distance. The measurement error of laboratory test is about 0.0033% of the object distance for local three-dimensional displacement measurement test. Test and analysis results of field test display that in-plane displacement error is only 0.12 mm, and the out-of-plane error is 1.1 mm for 20 m × 30 m measuring range. The out-of-plane error is only about 10 PPM of the object distance. These test and analysis results show that this proposed method can achieve very high accuracy under small displacement for both of laboratory and field tests.     

Detecting latent referential articles based on their vitality performance in the latest 2 years

In this paper, we propose a methodology to detect latent referential articles through a universal, citation-based investigation. We discuss articles’ dynamic vitality performance, concealed in their citation distributions, in order to understand the mechanisms that govern which articles are likely to be referenced in the future. Articles have diverse vitality performances expressed in the amount of citations obtained in different time periods. Through an examination of the correlation between articles’ future citation count and their past citations, we establish the optimal time period during which it is best to forecast articles’ future referential possibilities. The results show that the latest 2 years is the optimal time period. In other words, the correlation between the articles’ future citation count and their past citation count reaches a maximum value in the most recent 2-year period. The articles with a higher vitality performance in the most recent 2 years have a higher ratio of being cited as references in the future. These results help, not only, in understanding mechanisms of generating references, but also provide an additional indicator for decision makers to evaluate the academic performance of individuals according to their citation performance in the latest 2 years.     

Assessing obliteration by incorporation in a full-text database: JSTOR,Economics, and the concept of “bounded rationality”

To evaluate the usefulness of a full-text database as a source for assessing obliteration by incorporation (OBI), 3,707 article records including the catchphrases “bounded rationality” and/or “boundedly rational” (connected with the work of H. A. Simon) in the article text were retrieved from JSTOR, a full-text database with broad disciplinary coverage. Two subsets were analyzed—a 10 % systematic sample of all records and a set of all articles in Economics journals (with the addition of the Journal of Economic Theory). A majority of articles in the 10 % sample came from Economics and Management journals, while Psychology was poorly represented. In the 10 % sample, based on the percentage of true implicit citations between 1992 and 2009 in the 80 % of records that had a catchphrase in the body of the article, rather than just in the reference list, annual OBI ranged from 0 to 70 % (mean 33 %) with no discernible trend. The Economics articles showed a narrower range of OBI—fluctuating around 40 % implicit citations over the same time period. In both data sets, a large proportion of indirect citations were to sources that themselves cited a relevant work by Simon. Over 90 % of the articles in both the 10 % sample and the economics journal set would not have been retrieved with a database record search because they lacked the catchphrase in the record fields.     

Modeling Solids Friction for Dense-Phase Pneumatic Conveying of Powders

This article results from an ongoing investigation aimed at developing a new validated test-design procedure for the accurate prediction of pressure drop for dense-phase pneumatic conveying of powders. Models for combined pressure drop coefficient (“K”) for solids-gas mixture were derived using the concept of “suspension density” by using the steady-state “straight pipe” pressure drop data between two different tapping locations of the same pipe and also for two different diameter pipes. It was observed that the derived models were different depending on the location of tapping points (for the same pipe) and selected pipe diameters. The derived models were then evaluated by predicting the pressure drop for pipelines with various diameters or lengths (69 mm I.D. × 168 m, 105 mm I.D. × 168 m, 69 mm I.D. × 554 m) for the conveying of power station fly ash. A comparison between the predicted pneumatic conveying characteristics (PCC) and the experimental plots showed that the models resulted in significant over-predictions. In the second part of the article, the “system” approach of scaleup was evaluated. “Total” pipeline pressure drop characteristics for test-rig pipelines were scaled up to predict the PCC for larger/longer pipes. It was found that the “system” approach generally resulted in grossly inaccurate predictions. It was concluded that further studies are needed for a better understanding of the solids-gas flow mechanism under dense-phase conditions.     

Irradiation effects on AlGaN HFET devices and GaN layers

AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1 × 10⁷ to 1 × 10¹³ cm^?2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1 × 10¹⁰ cm^?2 resulted in a small reduction of 2% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5 × 10¹⁰ cm^?2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1 × 10¹² cm^?2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1 × 10¹² cm^?2. The device results and GaN layer properties are strongly correlated.     

Thermosensitive luminous fibers based on cresol red-boric acid reversible thermochromic pigments

In this study, thermosensitive luminous fibers (TLFs) were prepared by wet spinning, using polyacrylonitrile as the filament material and rare-earth long-afterglow luminescent materials as the optical source. Reversible thermochromic cresol red-boric acid (CB) pigment in the TFLs served as the luminescence conversion agent. The reflectivity curves and fluorescence spectra were recorded at 25 and 65 °C to investigate the thermosensitive characteristics of the TLFs. The results demonstrated that CB pigment functioned as a luminescent conversion agent that could convert the luminescence of rare-earth luminescent materials depending on the temperature. The luminescence of the TLFs can be converted from blue to fuchsia upon changing their temperature due to the structural transformation of the CB dye. The thermosensitivity can also be verified by observing the TLFs in water at 65 °C with the naked eye.     

Microstructure and rheological properties of titanium carbide-coated carbon black particles synthesised from molten salt

Homogeneous titanium carbide (TiC) coatings were prepared on carbon black (CB) particles by firing them with metallic titanium (Ti) powder in KCl or KCl–LiCl for 4 h at 750–850 °C. As-prepared TiC-coated CB retained the spherical shape of as-received CB, indicating that the ‘template-growth’ mechanism had dominated the reaction process. TiC coating thickness could be readily tailored by simply adjusting the Ti to CB ratio (Ti/C) of the initial starting mixture. The true density of TiC-coated CB particles increased with Ti/C, reducing the density difference between them and other aggregates used in castable systems and potentially improving the castables consistency. Zeta potential measurement, sedimentation comparison and rheology testing revealed that water-wettability and dispersivity of CB were improved significantly after TiC coating.     

Fast response and low power consumption 1×2 thermo-optic switch based on dielectric-loaded surface plasmon polariton waveguides

Abstract

In this paper, we present a 1 × 2 thermo-optic (TO) switch based on the integration of the dielectric-loaded surface plasmon polariton (SPP) waveguides with the silicon nanowires. Liquid-curable fluorinated resin (LFR) made of perfluorinated polymer was adopted as the ridge, which has a TO coefficient twice more than that of polymethyl methacrylate, leading to a significant decrease in the power consumption. It was shown that the response time of the dielectric-loaded SPP waveguide could be improved through optimizing the dimensions of the LFR polymer ridge without loss of relative high figure of merit and large confinement factor. Performance characteristics of such a 1 × 2 TO switch operating at a telecom wavelength of 1550 nm was investigated theoretically from the analysis of both heat and optical fields. The results reveal that a switching power as low as 7 mW and an extremely short switching time (with rise time of 3 μs and fall time of 6.7 μs) could be achieved with the proposed dielectric-loaded SPP-based 1 × 2 TO switch. In addition, the crosstalk could be enhanced to at least 40 dB with the applied power of 7 mW at the wavelength of 1550 nm, and it could be retained to be above 20 dB in the wavelength spectrum of 1500–1600 nm during the on/off state.     

Synthesis and thermal analysis of aluminium nitride filled epoxy composites and its effective application as thermal interface material for LED applications

The improvement of heat conduction in any electronic devices has become a predominant issue in which effective heat dissipation is crucial to enhance the performance of packaged devices. This paper elucidates the application of thermally conductive particles filled composites as thermal interface material for LEDs. Present work aims on reducing the junction temperature and thermal resistance of the device under test with heavily filled ceramic-epoxy composite as the interface material between the device and metal substrate. Silane treated aluminium nitride (AlN) powder was studied for its feasibility as the filler material. The thermal conductivity values obtained by hot disc method (ISO/DIS 22007-2.2) were 0.66, 0.54 and 0.44 W/mK for 60, 50 and 40 wt% AlN filled epoxy composites respectively which were described well by thermal transient measurement of LEDs. The junction temperature and total thermal resistance of the thermal set up was reduced significantly with increased filler loading. The least junction to ambient thermal resistance (R_thJ-A) was achieved for 60 wt% followed by 50 and 40 wt% AlN filled TIM with the values of 24.8, 31.98 and 34.64 K/W respectively. Characteristics of the AlN filled composites for LED applications are discussed extensively in terms of thermogravimetric and thermo-mechanical analysis.     

Surface hardening in N<Superscript>+</Superscript> implanted polycarbonate

The influence of low energy nitrogen ions on the surface hardness of polycarbonate has been studied by implanting some of these specimens with 100 keV N⁺ ions at a beam current of 1 μA/cm² in the dose range of 1 × 10¹⁵ to 1 × 10¹⁷ ions cm^?2. Knoop microhardness has been found to be increased nearly 24 times at a load of 9.8 mN, for the dose of 1 × 10¹⁷ ions cm^?2. The structural changes occurred in implanted specimens were studied by Raman analysis, UV–Visible spectroscopy, and X-ray diffraction techniques. Raman studies point toward the formation of a structure resembling hydrogenated amorphous carbon. Disordering in the surface structure (I _D/I _G ratio) has also been found to increase with ion fluence using Raman technique. UV–Visible spectroscopic analysis shows a clear enhancement in Urbach energy (disorder parameter) from a value of 0.61 eV (virgin sample) to 1.72 eV (at a fluence of 1 × 10¹⁷ N⁺ cm^?2) with increasing ion dose. The increase in Urbach energy has been found to be correlated linearly with the increase in Knoop microhardness number. Results of X-ray diffraction analysis also indicate disordering in implanted layers as a result of implantation. In the present work, the possible mechanism behind the formation of harder surfaces due to implantation has been discussed in detail.